Hemodynamic effects of different H2-receptor antagonists.

In a randomized, placebo-controlled, double-blind study, 10 healthy volunteers were treated orally once a day for 1 week each with placebo, 800 mg cimetidine, 300 mg ranitidine, and 40 mg famotidine. On the seventh treatment day, heart rate, blood pressure, systolic time intervals, and impedance cardiography were measured before the morning dose and at 2, 6, 12, and 24 hours after the morning dose. Heart rate and blood pressure were not markedly altered by any of the H2-receptor antagonists compared with the findings for placebo. Cimetidine and ranitidine did not markedly alter parameters of systolic time interval and impedance cardiography compared with placebo in contrast to famotidine, which significantly decreased stroke volume, cardiac output, and the Heather Index in impedance cardiography (p less than 0.05) and also significantly increased the ratio of the preejection period to the left ventricular ejection time in systolic time interval (p less than 0.05) 2 hours after the morning dose. Six hours after administration, most of these alterations could no longer be detected. The observed changes in hemodynamic parameters confirm that famotidine exerts negative effects on cardiac performance, whereas such influences could not be shown for cimetidine and ranitidine.